The last of the three APIs a generated module refers to. 22 UI entry
points and 7 dialog types, all built on the existing IUiChannel and its
message records.
Every 4GL interactive statement lowers to the same shape:
using (var d = UI.CreateX(...)) {
...configure...
while (d.Run()) { switch (d.GetEventID()) { case 3: ... } }
}
so UILib_Dialog owns that loop and each dialog says only how its own
clauses resolve. Clause ids are allocated by the generator as it walks
the source; -1 means the client did something no clause claimed, which
the generated switch falls through on - the same as 4GL, where an
unhandled key does nothing.
UILib_Menu COMMAND, BEFORE MENU, NEXT/SHOW/HIDE OPTION - which
address an option by its text, as 4GL does
UILib_Prompt PROMPT ... FOR
UILib_Input INPUT, with the BEFORE/AFTER FIELD clauses
UILib_InputArray INPUT ARRAY, plus ARR_CURR and SCR_LINE
UILib_Construct CONSTRUCT, returning the WHERE fragment
UILib_DisplayArray, UILib_keylist, FormField, FglWindowAttribute
The two INPUT bindings are the whole data path: one fills InBind from
the program's variables, the other reads RSet back into them. RSet is
an ASqlResult, the same type a FETCH returns, so an INPUT reads its
fields back with the same GetData calls - which is right, because in
4GL a screen record and a table row are the same thing. FglRow gained
a constructor from a UI event's field values to make that work.
UI is an instance property on FglModule, like SQL, so the channel and
the dialog contexts belong to the session.
DISPLAYTO was wrong and is now right. The generated protocol stub
carried its values as one opaque string; the real message sends the
field list and the values as two parallel arrays, neither
null-terminated, with a numeric ATTRIBUTE of -1 when the statement
named none, and values tagged with the 4GL type code the client
formats by. It was found by reading lib/libui/ui_json/json.c and then
confirmed against the live C runtime - the first version of this was
modelled on uilib.c, which is a different backend and disagrees.
It is the single most common thing a generated program sends - 83 call
sites in the demo corpus - so the UI probe now covers it: two fields,
two 4GL types, and the blank padding a CHAR keeps on its way to the
form. The two streams agree byte for byte.
A protocol guard test earned its keep here, failing the moment two
records claimed the DISPLAYTO verb.
Fidelity: 27 semantics, 9 UI messages, 30 USING, the 66-line report and
5 end-to-end programs all agree with C. 203 runtime tests pass.
